Open Access
Visible-light-driven photocatalytic degradation of organic dyes using a TiO2 and waste-based carbon dots nanocomposite
(Elsevier, 2025-05-20) Sendão, Ricardo M.S.; Algarra González, Manuel; Lázaro-Martínez, Juan; Brandão, Ana T.S.C.; Gil Bravo, Antonio; Pereira, Carlos; Esteves da Silva, Joaquim C.G.; Pinto da Silva, Luís; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
Herein we report a visible-light-active photocatalytic nanocomposite (NC50:50) prepared from carbon dots (CDs) and TiO2 nanoparticles, which was applied to the photodegradation of organic dyes in water. The CDs incorporated corn stover, a major agricultural waste, and were prepared via hydrothermal treatment. Using a visible-light irradiation source and the dye methylene blue as a representative of the organic dyes class, we observed that a 374% enhancement of the catalytic performance was achieved by adding CDs relative to bare TiO2. This was possible due to increased visible-light absorption and better photonic efficiency. Tests using reactive species scavengers indicated that three active species (superoxide anion, hydroxyl radicals, and electrons) were responsible for the photodegradation process, differing from bare TiO2 in which only the hydroxyl radical has a relevant role. Photocatalytic degradation was also observed toward Rhodamine B, Orange II and Methyl Orange. Finally, we performed a life cycle assessment (LCA) study to assess and analyse the associated environmental impacts of NC50:50 compared with other alternatives, which revealed that NC50:50 is the alternative resulting in the least environmental impacts. In summary, NC50:50 could, under visible-light irradiation, efficiently remove different organic dyes while incorporating organic waste materials and reducing the impacts associated with their use. We expect that this study provides a base for a more environmentally sustainable design of visible-light-active photocatalysts via waste upcycling.
Open Access
A sustainable approach for the valorization of lignocellulosic biomass in active photo- and electrocatalyst carbon dots
(Springer, 2024) Jorge, Herculys Bernardo; Gier Della-Rocca, Daniela; Herrera, Elisa Gabriela; Rodríguez-Castellón, Enrique; Gil Bravo, Antonio; Amorim, Suélen Maria de; Winiarski, Joao Paulo; Vieira, Iolanda da Cruz; Peralta Muniz Moreira, Regina de Fatima; Algarra González, Manuel; Peralta, Roselyn Aparecida; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
The recovery or degradation of organic wastes in the circular economy concept continues to be environmental protection challenges. In this study, we proposed a metal catalyst free production of useful non-doped (CDs) and nitrogen doped carbon dots (N-CDs) nanoparticles, generated from a greener hydrothermal top-down method, using paper scraps solid organic wastes from the pulp and paper industry. Both materials were fully characterized. At the same time, these high-added value materials were used as catalysts for the photocatalytic degradation of pollutants and for generating hydrogen through hydrogen evolution reaction (HER). The morphological study revealed the presence of nanoparticles with a higher carbon content than the raw biomass, from 13 to 51 wt% as assessed by X-ray photoelectron spectroscopy (XPS), ranging in size from 4.4 to 6.8 nm. The ability of these materials to catalyze the photodegradation of 4-nitrophenol has been tentatively investigated. The N-CDs proved to be more active than undoped-CDs to degrade 4-nitrophenol due to the smaller bandgap and more active sites available which will also accept the transferred electrons for H2 generation or 4-nitrophenol reduction.

Gil Bravo, Antonio

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